Solar Developer Has Plan to Turn Oil Wells Into Energy Storage

A California developer of concentrated solar power (CSP) systems has announced an innovation that it says combines the company's technologies to turn existing oil wells into energy storage sites that can provide clean energy.

Hyperlight Energy on Feb. 24 said it was launching Tectonic Sun, an electricity generation technology that when paired with the company's Hylux solar thermal solution can provide zero-carbon electricity" from oil wells while reducing emissions during the extraction process at enhanced oil recovery [EOR] sites." Hyperlight on Thursday said the new system is capable of providing emissions-free power with 80% capacity factor for use at any time of day or night throughout the year." (Go here to view a video detailing how the technology works.)

The company has a technology demonstration project, Tectonic Sun Alpha, at a Hathaway oil drilling site in Bakersfield, California. Hathaway is an independent, Bakersfield-based drilling company that operates six oil and gas fields in Kern County, California.

Repurposing Oil Wells

The industry is increasingly embracing the concept of cost reduction through repurposing oil wells, as shown by the Department of Energy's Geothermal Technology Office [GTO] recently announced group of projects aiming to use old oil wells to access traditional geothermal-based heat, and Southern Company's research collaboration with innovator Petrolern, to Convert Oil Wells to Geothermal Resources'," said John King, CEO of Hyperlight Energy. (The DOE last year announced as much as $46 million to support other geothermal projects.)

Hyperlight in a news release said the application of CSP thermal energy for power generation and emissions reduction is an industry first," adding that the company estimates the statewide potential [energy] storage capacity of its technology" would exceed the combined generation from California's natural gas-fired power plants. Hyperlight said the Bakersfield demonstration builds on groundbreaking analysis work on geological thermal energy storage (GeoTES) performed by Hyperlight partner, [the] National Renewable Energy Laboratory [NREL]."

Other technologies are being utilized to generate power from oil and gas wells, including the use of geothermal. The technology promises to make bitcoin mining more environmentally friendly.

King told POWER, We are referencing an analysis done by NREL in this seminal paper [purchase required for the full paper] from last year. We worked with NREL to establish estimates for scaling this up at EOR retrofit sites." King said an optimal configuration, based on the NREL analysis, establishes a figure for analysis of 36.5 MWe for a representative plant. The paper assumed 24 wells per MWe. NREL and Hyperlight bumped this up to 50 wells per MWe for no particular technical reason other than simple conservatism. We then assumed [again, for no reason other than conservatism] that only 1 in 5 of the 100,000 wells in California could be used for this application at 80% capacity factor, or 7,000 hours per year."

King provided this calculation: 7,000 hours x .75 MWhe/well x 20,000 wells = 105 TWhe/year.

He noted the calculation yields >100 TWhe of power production per year. The total combined output of all the natural gas power plants in the state, combined, was 98 TWhe in 2018," according to the state. King said the NREL analysis showed the energy capacity of a typical GeoTES installation is about 146,000 MWhe, with a storage duration of 4,000 hours-about six months of energy storage-at a much smaller cost than any other approach (NREL's paper estimated 10/kWh to 16/kWh). Hyperlight in its Thursday news release said that Unlike other emerging technologies that offer only hours or days of storage based on one or two years of data and modeling, EOR has six decades of operation at scale by the world's largest energy companies, with existing study data showing breakthrough round-trip thermal efficiency."

King said the NREL analysis was for a greenfield project," and his company's technology would bring costs down even more. We are going in at EOR retrofits, where the wells and thermal infrastructure are already built, and where there are existing cogen plants with transmission infrastructure in place," he said. Further, we are leveraging the LCFS [California's Low Carbon Fuel Standard program] to offset the cost of the CSP field. All of these factors are what combine to significantly reduce the costs below the NREL-estimated 10 to 16/kWh, down to 4 to 8/kWh."

Different from Other Geothermal Well Projects

King told POWER his company's technology differs from other geothermal projects at oil and gas wells, such as those being developed for bitcoin mining. I am familiar with it in terms of the surplus natural gas at a lot of sites, which is often simply flared off," King said. If one were to put a microturbine at a site to burn that same surplus gas to generate power, you could use that power to perform the mining."

Capstone Green Energy Corp. on Feb. 22 announced that its southern U.S. distributor, Lone Star Power Solutions, has contracted with a remote data center in Louisiana on the use of a Capstone C1000S microturbine system, the second such system at that site to support bitcoin mining. The customer was not named, but Capstone said the system is located on an oil and gas well and handles large-volume blockchain and cryptocurrency mining. The microturbine uses well-produced gas, or waste gas, that might otherwise be flared.

King said Hyperlight's Tectonic Sun Alpha is different in multiple, important ways," namely through its use of solar and geothermal power:

• The Department of Energy's GTO is exclusively focusing on oil/gas wells where the rock is already hot, and the existence of the wells provides access that would not otherwise be feasible. It is not adding heat with a surface technology the way Hyperlight is with its Hylux/Tectonic Sun platform. This means that Hylux/Tectonic Sun is not restricted to geology that is already hot."
• The bitcoin mining example still relies on burning fossil fuels, whereas with Hylux/Tectonic Sun we are using zero-carbon solar heat at the beginning of the process and creating zero-carbon power at the end of the process."
• We are focusing on EOR projects that are still in service. This is both a technical and business innovation. It is a technical innovation because it allows a dual use of the existing EOR sites enabling two simultaneous low-carbon technical applications. Second, it is a business innovation because it decarbonizes existing oil production, which is a necessary part of the energy transition, and improves project economics by tapping into the incentives offered by the [LCFS] program."

The methods of action of thermal EOR (tEOR) and CO₂ EOR are fundamentally different," King said. In tEOR, sensible heat is used to reduce the specific gravity of heavy oil so it can flow to the production wells-and CSP has already been technically proven for this application. CO₂ EOR largely relies on pressure to force the oil to the production wells, and CCS [carbon capture and storage] is much earlier in development stages for this application. Thermal losses are a lot lower than pressure losses at these sites, so roundtrip energy efficiency in tEOR can be much higher than for CO₂ EOR."

He added, In this approach we are using geothermal as the energy storage medium, not the power generation source. The solar-injected heat naturally captured in the rock surrounding the oil wells is what is being leveraged to generate power for applications beyond the oil/gas well operations. You don't need to only do this where the rock is already hot."

The Hyperlight project comes as California looks for more renewable power generation, with state regulators calling for at least 1 GW from emerging and nascent technologies as part of an overall goal of 11.5 GW of clean energy. The California Dept. of Conservation said the state's oil and gas industry has more than 100,000 wells. Hyperlight on Thursday said having solar power infrastructure in place at wells provides for renewable energy output even after EOR activity ends.

Tectonic Sun Alpha reshapes the way we think about long-duration storage and has transformative potential not just for California's grid, but for the oil and gas industry throughout the state," said King. Unlike oil and gas projects which eventually run dry, a GeoTES project will never run out of sunlight. We believe Tectonic Sun Alpha can offer a blueprint to retrofit the tens of thousands of existing oil wells in California with solar thermal energy to produce a significant new source of cost effective, non-intermittent clean power."

-Darrell Proctor is a senior associate editor for POWER (@POWERmagazine).

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